I am unable to use a writable store when using shares, the documentation states that the path at microvm.writableStoreOverlay must be writable, and #20 mentions that this should work with a writabe overlay on share.

I can get a writable store using microvm.volumes, i.e.

{ config, ... }:
{
  microvm.writableStoreOverlay = "/nix/.rw-store";
  microvm.volumes = [{
    mountPoint = config.microvm.writableStoreOverlay;
    image = "store.img";
    size = 2000;
  }];
}

however trying to use a share instead with something like:

{ config, ... }:
{
  microvm.writableStoreOverlay = "/nix/.rw-store";
  microvm.shares = [
    {
      source = "/tmp/test-writable-store";
      mountPoint = config.microvm.writableStoreOverlay;
      tag = "rw-store";
      proto = "virtiofs";
      socket = "nix-store-rw.sock";
    }
  ];
}

results in a VM which does not boot, stating that the upper fs is missing required features.

mounting overlay filesystem on /nix/store...
[    0.324712] overlayfs: upper fs missing required features.
mount: mounting overlay on /mnt-root/nix/store failed: Invalid argument

This was tested with cloud-hypervisor specifically.

I couldn't find a test or example which shows this usecase, is this meant to be supported or am I doing something wrong?